U.S. patent application number 12/154878 was filed with the patent office on 2009-12-03 for glass packages and methods of controlling laser beam characteristics for sealing them.
Invention is credited to Stephan Lvovich Logunov, John David Lorey, Vitor Marino Schneider.
Application Number | 20090295277 12/154878 |
Document ID | / |
Family ID | 41378939 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090295277 |
Kind Code |
A1 |
Logunov; Stephan Lvovich ;
et al. |
December 3, 2009 |
Glass packages and methods of controlling laser beam
characteristics for sealing them
Abstract
A display device (10) including a first substrate (12), a second
substrate (16), an OLED element (18), and a wall (14) that contains
glass. A sealed portion (6) is formed in the wall and between the
first substrate and the second substrate so as to produce a
hermetic seal. The sealed portion is disposed in the wall so that
unsealed portions (7,8) are disposed on opposite sides of the
sealed portion. A width (3) of the sealed portion is from about 35%
to about 77.3% of a width (2) of the wall. The sealed portion may
be formed by heating the wall with a laser beam (32) so that a
thickness (1) of the wall lies within the depth of focus (34) of
the laser beam. Further, the width (36) of the laser beam can be
less than or equal to the width of the wall.
Inventors: |
Logunov; Stephan Lvovich;
(Corning, NY) ; Lorey; John David; (Corning,
NY) ; Schneider; Vitor Marino; (Painted Post,
NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
41378939 |
Appl. No.: |
12/154878 |
Filed: |
May 28, 2008 |
Current U.S.
Class: |
313/504 ; 445/25;
445/3 |
Current CPC
Class: |
H01J 9/261 20130101;
H01L 51/5246 20130101; H01L 51/56 20130101; H01J 9/40 20130101 |
Class at
Publication: |
313/504 ; 445/25;
445/3 |
International
Class: |
H01J 9/26 20060101
H01J009/26; H01J 1/62 20060101 H01J001/62; H01T 21/06 20060101
H01T021/06 |
Claims
1. A device comprising: a first substrate; a second substrate; and
a wall coupling the first substrate to the second substrate, the
wall comprising a width, a thickness, a sealed portion, and
unsealed portions located on opposite sides of the sealed portion,
wherein the wall contains glass, and wherein a width of the sealed
portion comprises from about 35% to about 77.3% of the width of the
wall.
2. The device according to claim 1, wherein the width of the sealed
portion comprises from about 50% to about 75% of the width of the
wall.
3. The device according to claim 1, wherein the sealed portion is
disposed in the wall so that the unsealed portions are
substantially equal in width.
4. The device according to claim 1 further comprising: at least one
organic element disposed between the first substrate and the second
substrate, wherein the sealed portion forms a hermetic seal between
the first substrate and the second substrate so as to protect the
at least one organic element located between the first substrate
and the second substrate.
5. A method of sealing two substrates coupled by a wall including a
thickness, the method of sealing comprising the steps of: directing
a laser beam toward the wall, the laser beam comprising a depth of
focus, wherein the laser beam is positioned relative to the wall so
that the wall thickness lies within the depth of focus of the laser
beam.
6. The method of claim 5, wherein the laser beam further comprises
a beam width, wherein the wall further comprises a width, and the
beam width is less than or equal to the width of the wall.
7. The method of claim 6, wherein the laser beam further comprises
a beam width having an intensity profile, wherein the wall further
comprises a width, and the intensity profile produces in the wall a
sealed portion having a width, wherein the width of the sealed
portion comprises from about 35% to about 77.3% of the width of the
wall.
8. The method of claim 5, wherein the laser beam further comprises
a beam width, wherein the wall further comprises a width, wherein
the beam width is larger than the width of the wall, and the method
further comprises disposing a beam-shaping plate having an aperture
therein so that the laser beam is aligned to pass through the
aperture prior to reaching the wall, wherein the aperture has a
width that is less than or equal to the width of the wall.
9. The method of claim 8, further comprising traversing the laser
beam relative to the wall, and traversing the beam-shaping plate
along with the laser beam so as to maintain alignment between the
laser beam and the aperture.
10. The method of claim 8, wherein the beam-shaping plate is
disposed within the depth of focus of the laser beam.
11. The method of claim 5, wherein the laser beam comprises a
flat-top laser beam.
12. The method of claim 5, wherein the laser beam further comprises
a footprint having a center-portion, wherein an area of the
center-portion is less than an area on either side of the
center-portion.
13. The method of claim 5, wherein the step of directing the laser
beam further comprises directing the laser beam through a delivery
system, wherein the delivery system comprises a lens for focusing
the laser beam, and the method further comprises at least one of:
measuring temperature of the wall with a thermal monitoring device
via the lens; and obtaining a visual image of the wall with an
imaging device via the lens.
14. A method of sealing a two substrates coupled by a wall
including a width, the method of sealing comprising the steps of:
directing a laser beam toward the wall, the laser beam comprising a
beam width, the beam width including an intensity profile, the
intensity profile comprising a maximum intensity portion sufficient
to form a sealed portion in the wall and lesser intensity portions
that do not form a sealed portion in the wall, wherein the laser
beam is positioned relative to the wall so that the beam width is
less than or equal to the wall width.
15. The method of claim 14, wherein the maximum intensity portion
of the intensity profile produces in the wall a sealed portion
having a width, wherein the width of the sealed portion comprises
from about 35% to about 77.3% of the width of the wall.
16. The method of claim 14, wherein the laser beam comprises a
flat-top laser beam.
17. The method of claim 14, wherein the laser beam further
comprises a footprint having a center-portion, wherein an area of
the center-portion is less than an area on either side of the
center-portion.
18. The method of claim 14, wherein the wall further comprises a
thickness, wherein the laser beam further comprises a depth of
focus, and the wall thickness lies within the depth of focus of the
laser beam.
19. The method of claim 18, wherein the step of directing the laser
beam further comprises directing the laser beam through a delivery
system, wherein the delivery system comprises a lens for focusing
the laser beam, and the method further comprises at least one of:
measuring temperature of the wall with a thermal monitoring device
via the lens; and obtaining a visual image of the wall with an
imaging device via the lens.
Description
BACKGROUND
Field of the Invention
[0001] This invention is generally directed to methods for sealing
glass packages for encapsulating a display element such as used for
glass substrates for flat panel display devices, for example,
organic light emitting diode (OLED) display devices. Also disclosed
are glass packages formed according to aspects of the disclosed
methods.
TECHNICAL BACKGROUND
[0002] Laser heating of a wall, disposed between a first substrate
and a second substrate, and formed from dispensed frit that has
been sintered, to form hermetic seals for display devices has
conventionally been used.
[0003] One current laser sealing method is designed so that the
laser beam is defocused and its size is controlled by the distance
from a laser delivery system to the display device. However,
because the laser beam size is controlled by the distance between
the laser delivery system and the display device, this system is
sensitive to changes in this distance as produced by vibrations and
imperfections in the laser delivery system, for example.
[0004] Also, some laser sealing methods required use of a laser
mask. The reason for having a laser mask was to achieve the widest
possible seal width and protect nearby device elements (such as
thin film electronics, OLED elements or electrodes, for example)
from direct laser exposure. The edges of the wall may be at a lower
temperature than the center of the wall due to the energy
distribution (intensity profile) in the laser beam. This
temperature distribution can be improved by increasing beam
diameter. In doing so, however, the device elements may be exposed
to laser radiation creating heat damage.
[0005] In one sealing method that uses a mask, a mask sheet is
disposed over the device substrate so as to expose the wall along
its entire perimeter so that the wall may be heated with a laser.
In general, the mask is of a similar size as the substrate. This
masking method works effectively, but a drawback is the need to
have an additional piece of glass with the mask disposed thereon,
which needs to be made and aligned with the OLED substrate. In
addition, using weights or an application of sealing force with a
mask present reduces the effectiveness of such pressure
applications.
SUMMARY
[0006] In one embodiment, a wall is presented. The wall includes a
width, a thickness, and edges. Further, the wall contains glass,
and is disposed between first and second substrates. A sealed
portion of the wall couples the first and second substrates to one
another. The width of the sealed portion is from about 35% to about
77.3% of the width of the wall.
[0007] A laser beam is directed at the wall to form the sealed
portion in the wall. The laser beam includes two specific
characteristics, namely, a depth of focus and an intensity
profile.
[0008] The laser beam depth of focus extends vertically over a
range of the laser beam. In one embodiment, the depth of focus may
be described as the portion of the laser beam that includes a
substantially constant width and a consistent power density over
the vertical range of the laser beam. The vertical range of the
laser beam is located about a focal point of the laser beam.
[0009] An intensity profile of the laser beam is defined across the
width of the laser beam. The intensity profile includes a maximum
intensity portion near the center of the width of the laser beam,
and lesser intensity portions outside of the maximum intensity
portion. The maximum intensity portion is that portion of the laser
beam that has an intensity sufficiently high enough to produce the
sealed portion in the wall. The lesser intensity portions are
located outside of the area defined by the maximum intensity
portion. The lesser intensity portions do not have an intensity
that is sufficiently high enough to produce a sealed portion in the
wall. The width of the laser beam is that at which the intensity
drops to less than about 2-3% of its maximum value.
[0010] In one embodiment, the intensity profile is described by a
Gaussian distribution with a center area portion corresponding to
the maximum intensity portion of the laser beam that is suitable
for producing the sealed portion of the wall. The side lobes in the
Gaussian distribution correspond to lesser intensity portions of
the laser beam outside of the maximum intensity portion. The lesser
intensity portions do not have an intensity sufficiently high
enough to produce a sealed portion in the wall. In one embodiment,
the resulting wall includes sealed and unsealed portions, wherein
the sealed portion has a width that is between 35% to 77.3% of the
width of the wall. The side lobes are directed toward the wall such
that the radiation produced by the side lobes of the laser beam is
absorbed by the unsealed portions of the wall. Thus, the unsealed
portions of the wall protect the device elements (such as
electrodes and OLED elements) thereby eliminating the need for a
mask.
[0011] In one embodiment, the laser beam is directed toward the
wall such that the entire thickness of the wall is positioned
within the depth of focus of the laser beam. In a second
embodiment, the laser beam is directed at the wall such that the
laser beam width is less than or equal to the width of the wall. As
such the maximum intensity portion will seal the center portion of
the wall producing a wall with a sealed center portion that is
flanked by two unsealed portions one on each side of the sealed
portion. It should be appreciated that while these two embodiments
directed to using a laser beam to form a sealed portion in the wall
are described separately, in another embodiment, both of these
embodiments may be combined.
[0012] By sealing a wall of a device with a laser beam so that the
thickness of the wall lies within the depth of focus of the laser
beam, uniformity of the seal is less sensitive to vibrations and
imperfections in the delivery system, as well as less sensitive to
changes in the distance between the delivery system and the display
device.
[0013] The mask can be eliminated by sealing a wall of a device
with a laser beam having a width that is less than or equal to the
width of the wall, wherein the width of the laser beam corresponds
to that at which the intensity drops to less than about 2-3% of its
peak value. Elimination of a laser mask is advantageous from the
perspectives of simplicity of the process and cost
effectiveness.
[0014] Additional features and advantages of the invention will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from the
description or recognized by practicing the invention as described
in the written description and claims hereof, as well as the
appended drawings.
[0015] According to one aspect, there is provided a device
including a first substrate, a second substrate, and a wall
coupling the first substrate to the second substrate. The wall has
a width, a thickness, a sealed portion, unsealed portions located
on opposite sides of the sealed portion, and contains glass. The
width of the sealed portion is from about 35% to about 77.3% of the
width of the wall.
[0016] According to another aspect, the width of the sealed portion
is from about 50% to about 75% of the width of the wall.
[0017] According to another aspect, the sealed portion is disposed
in the wall so that the unsealed portions are substantially equal
in width.
[0018] According to another aspect, there is provided a method of
sealing two substrates coupled by a wall including a width, and a
thickness. The method of sealing includes directing a laser beam
toward the wall. The laser beam has a depth of focus and a beam
width, wherein the beam width includes an intensity profile. The
laser beam is positioned relative to the wall so that the wall
thickness lies within the depth of focus of the laser beam.
[0019] According to another aspect, the laser beam intensity
profile produces in the wall a sealed portion having a width,
wherein the width of the sealed portion is from about 35% to about
77.3% of the width of the wall.
[0020] According to another aspect, the laser beam width is less
than or equal to the width of the wall.
[0021] According to another aspect, the laser beam width is larger
than the width of the wall, and the method further includes
disposing a beam-shaping plate having an aperture therein so that
the laser beam is aligned to pass through the aperture prior to
reaching the wall. The aperture has a width that is less than or
equal to the width of the wall.
[0022] According to another aspect, the laser beam is traversed
relative to the wall, and the beam-shaping plate is traversed along
with the laser beam so as to maintain alignment between the laser
beam and the aperture.
[0023] According to another aspect, the beam-shaping plate is
disposed within the depth of focus of the laser beam.
[0024] According to another aspect, the laser beam is a flat-top
laser beam.
[0025] According to another aspect, the laser beam includes a
footprint having a center-portion, wherein an area of the
center-portion is less than an area on either side of the
center-portion.
[0026] According to another aspect, the laser beam is directed
through a delivery system. The delivery system includes a lens for
focusing the laser beam, and the method further includes at least
one of: measuring temperature of the wall with a thermal monitoring
device via the lens; and obtaining a visual image of the wall with
an imaging device via the lens.
[0027] According to another aspect, there is provided a method of
sealing a two substrates coupled by a wall including a width, and a
thickness. The method of sealing includes directing a laser beam
toward the wall. The laser beam has a depth of focus and a beam
width, wherein the beam width includes an intensity profile. The
intensity profile includes a maximum intensity portion sufficient
to form a sealed portion in the wall and lesser intensity portions
that do not form a sealed portion in the wall. The laser beam is
positioned relative to the wall so that the beam width is less than
or equal to the wall width.
[0028] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary of the invention, and are intended to provide an overview
or framework to understanding the nature and character of the
invention as it is claimed.
[0029] The accompanying drawings are included to provide a further
understanding of principles of the invention, and are incorporated
in and constitute a part of this specification. The drawings
illustrate one or more embodiment(s), and together with the
description serve to explain the principles and operation of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a cross sectional side view of a display device
according to one embodiment.
[0031] FIG. 2 is a partial cross sectional side view of a display
device and a delivery system that may be used to direct a laser
beam for sealing the wall.
[0032] FIG. 3 is a partial cross sectional side view of a wall and
a laser beam used to seal the wall.
[0033] FIG. 4 is a top view of the wall and laser beam of FIG.
3.
[0034] FIG. 5 is a schematic diagram of a lens and laser beam
focused by the lens.
[0035] FIG. 6 is a graph showing laser beam width at various
distances from the focal point of the lens.
[0036] FIG. 7 is a graph of laser beam intensity at various
distances across the width of a wall, for a Gaussian beam, and
showing seal width in relation to the width of the wall according
to one example.
[0037] FIG. 8 is a graph of laser beam intensity at various
distances across the width of a wall, for a flat-top beam, and
showing seal width in relation to the width of the wall, according
to another example.
[0038] FIG. 9 is a graph of laser beam intensity at various
distances across the width of a wall, for a flat-top beam, and
showing seal width in relation to the width of the wall, according
to another example.
[0039] FIG. 10 is a graph showing the probability of failure at
various 4-point fracture loads for devices sealed with laser beams
having different characteristics.
[0040] FIG. 11 is a schematic view of a circular laser beam
footprint.
[0041] FIG. 12 is a schematic view of a square laser beam
footprint.
[0042] FIG. 13 is a schematic view of a cross-shaped laser beam
footprint.
[0043] FIG. 14 is a schematic view of a square-in-square laser beam
footprint.
[0044] FIG. 15 is a partial cross sectional side view of a display
device and a delivery system having a beam-shaping plate during a
sealing operation.
[0045] FIG. 16 is a schematic top view of a beam-shaping plate
having an aperture.
DETAILED DESCRIPTION
[0046] In the following detailed description, for purposes of
explanation and not limitation, example embodiments disclosing
specific details are set forth to provide a thorough understanding
of the principles of the present invention. However, it will be
apparent to one having ordinary skill in the art, having had the
benefit of the present disclosure, that the present invention may
be practiced in other embodiments that depart from the specific
details disclosed herein. Moreover, descriptions of well-known
devices, methods and materials may be omitted so as not to obscure
the description of the principles of the present invention.
Finally, wherever applicable, like reference numerals refer to like
elements.
[0047] Although the sealing techniques of the present invention are
described with respect to manufacturing a hermetically sealed
display device having an OLED element, it should be understood that
the same or similar sealing techniques can be used to seal two
glass plates to one another that can be used in a wide variety of
applications and devices. Accordingly, the sealing techniques of
the present invention should not be construed in a limited
manner.
[0048] The sealing techniques disclosed herein generally involve
controlling the characteristics of a laser beam, used to seal a
wall in a display device.
[0049] In one sealing technique, a focused laser beam is used to
seal the display device by heating the wall with the laser so that
the wall thickness is within the depth of focus of the laser beam.
A focused laser beam may have a depth of focus that allows better
tolerances for alignment of the delivery system with respect to the
display device and, therefore, is more immune to changes in
distance between the delivery system and the display device such as
due to vibrations and imperfections of the delivery system, for
example. In addition, operating within the depth of focus of the
laser beam is advantageous in that it is possible also to provide
an imaging device operating through the same delivery system as for
the laser beam and to provide a thermal monitoring device for
measuring the temperature of the sealing process, also operating
through the same delivery system as for the laser beam.
[0050] A second technique involves controlling the width and
intensity profile of the laser beam so that the width, at which the
laser beam intensity drops to less than about 2-3% of its maximum,
is less than the width of the wall. With this technique, a mask can
advantageously be eliminated.
[0051] In either technique, different laser beam footprint shapes
can be used to minimize the damage to the device elements while
keeping a good sealing strength and high hermeticity of the display
devices.
[0052] FIG. 1 is a partial cross sectional side view of a
hermetically sealed organic light emitting diode (OLED) display
device 10 in accordance with an embodiment of the present
invention. The display device 10 generally comprises a first
substrate 12, a wall 14, a second substrate 16, at least one OLED
element 18 and at least one electrode 20 in electrical contact with
the OLED element 18.
[0053] The first substrate 12 may be a transparent glass plate like
the ones manufactured and sold by Corning Incorporated under the
brand names of Code 1737 glass or Eagle 2000.TM. glass.
Alternatively, first substrate 12 can be any transparent glass
plate such as, for example, the ones manufactured and sold by Asahi
Glass Co. (e.g., OA10 glass and OA21 glass), Nippon Electric Glass
Co., NHTechno and Samsung Corning Precision Glass Co. Second
substrate 16 may be the same glass substrate as first substrate 12,
or second substrate 16 may be a non-transparent substrate.
[0054] Typically, OLED element 18 is in electrical contact with an
anode electrode and a cathode electrode. As used herein, electrode
20 in FIG. 1 represents either electrode. Although only a single
OLED element is shown for simplicity, display device 10 may have
many OLED elements disposed therein. The typical OLED element 18
includes one or more organic layers (not shown) and anode/cathode
electrodes. However, it should be readily appreciated by those
skilled in the art that any known OLED element 18 or future OLED
element 18 can be used in display device 10. In addition, it should
be appreciated that another type of thin film device can be
deposited besides OLED element 18. For example, thin film sensors
may be fabricated using the principles present invention.
[0055] The wall 14 contains glass, has a thickness 1, a width 2,
edges 4, 5 and is disposed between the first substrate 12 and
second substrate 16. See FIG. 1. Additionally, the wall 14 includes
a sealed portion 6 that is connected to first substrate 12 and to
second substrate 16 so as to form a hermetically sealed space in
which the OLED element 18 is disposed. The sealed portion 6 has a
seal width 3. On either side of the sealed portion 6, there are
unsealed portions 7 and 8 which may be sintered but do not form a
hermetic seal between the first 12 and second 16 substrates.
Although the wall 14 is shown as being rectangular in
cross-section, such is for the sake of simplicity alone. The
cross-sectional shape of the wall is not particularly limited. The
wall can be any deployment of material containing glass, and can
have any suitable cross-sectional shape so as to adequately
position the first substrate 12 relative to the second substrate
16.
[0056] Prior to sealing first substrate 12 to second substrate 16,
i.e., forming sealed portion 6, frit is deposited to form a wall 14
on first substrate 12, typically as a line of a frit paste
comprising a glass powder, a binder (usually organic) and/or a
liquid vehicle. The wall 14 is then heated to sinter the frit,
after which the second substrate 16 (including OLED element 18 and
electrodes 20) is placed on the wall 14 so as to sandwich the wall
14 between the first 12 and second 16 substrates. Subsequently, a
laser beam 32 is directed toward the wall 14 to form sealed portion
6.
[0057] Frit can be deposited onto first substrate 12 by
screen-printing or by a programmable auger robot which provides a
well-shaped pattern--to form wall 14--on first substrate 12. For
example, frit can be formed into a wall 14 approximately 1 mm away
from the free edges 13 of first substrate 12 as a line, or a
plurality of connected lines, and is typically deposited in the
shape of a closed frame. Again, the cross-sectional shape of the
wall is not particularly limited. The frit may be, for example, a
low temperature glass frit that has a substantial optical
absorption cross-section at a predetermined wavelength which
matches or substantially matches the operating wavelength of the
laser used in the sealing process. The frit may, for example,
contain one or more light absorbing ions chosen from the group
including iron, copper, vanadium, neodymium and combinations
thereof (for example). The frit may also include a filler (e.g., an
inversion filler or an additive filler) which changes the
coefficient of thermal expansion of the frit so that it matches or
substantially matches the coefficient of thermal expansions of
substrates 12 and 16. For a more detailed description regarding
exemplary frit compositions that may be used in this application,
reference is made to U.S. Pat. No. 6,998,776 entitled "Glass
Package that is Hermetically Sealed with a Frit and Method of
Fabrication", the contents of which are incorporated by reference
herein.
[0058] The wall 14 may be sintered prior to sealing first substrate
12 to second substrate 16. To accomplish this, the frit deposited
to form the wall 14 on first substrate 12 is heated so that the
wall 14 becomes attached to first substrate 12. Then, first
substrate 12 with wall 14 attached thereto can be placed in a
furnace which "fires" or consolidates the frit of the wall 14 at a
temperature that depends on the composition of the frit. During the
sintering phase, the frit of the wall 14 is heated and organic
binder materials contained within the frit are burned out.
[0059] The thickness 1 of the wall 14 is on the order of hundreds
of microns, depending on the application for display device 10. An
adequate but not overly thick wall allows the substrates to be
sealed from the backside of first substrate 12. If the wall 14 is
too thin it does not leave enough material to absorb the laser
radiation. If the wall 14 is too thick it will be able to absorb
enough energy at the first surface to melt, but will prevent the
necessary energy needed to melt the material of the wall 14 from
reaching the region of the wall proximate second substrate 16.
[0060] The sealing process includes placing first substrate 12,
with wall 14, on top of second substrate 16, with one or more OLED
elements 18 and one or more electrodes 20 deposited on the second
substrate 16, in such a manner that wall 14, the one or more OLED
elements 18, and electrodes 20 are sandwiched between the two
substrates 12 and 16 separated by wall 14. Mild pressure can be
applied to substrates 12 and 16 to keep them in contact during the
sealing process. A laser beam 32 is directed onto wall 14 through
first substrate 12 and heats the wall 14 such that the wall 14 at
least partially melts and forms sealed portion 6 that forms a
hermetic seal connecting and bonding substrate 12 to substrate 16.
The hermetic seal also protects OLED elements 18 by preventing
oxygen and moisture in the ambient environment from entering into
display device 10. A delivery system 30, as shown in FIG. 2 for
example, may be used to direct the laser beam 32 onto the wall
14.
[0061] For one exemplary embodiment, the laser beam 32 is shown in
relation to the wall 14 in FIGS. 3 and 4. FIG. 3 is a
cross-sectional view of the wall 14 as situated similarly to the
wall 14 shown on the right side of FIG. 1 but having a laser beam
32 superimposed thereon. FIG. 4 is a top view of the wall 14,
having a laser beam footprint 35 superimposed thereon. The first
substrate 12 and second substrate 16 are not shown in FIG. 3 for
sake of simplicity, but would be located on the top and bottom of
the wall 14 as those directions are shown in FIG. 3. As seen in
FIG. 3, the thickness 1 of the wall 14 lies within the depth of
focus 34 of the laser beam 32. As seen in FIG. 4, the laser beam 32
has a footprint 35 having a width 36 shown across the top of the
wall 14. It should be noted that the width 36 is the width of the
laser beam 32 at the point wherein the intensity drops to less than
about 2-3% of its peak value. The intensity of less than about 2-3%
of the maximum intensity is a value that is not expected to create
any damage to the OLED elements 18 in the display device 10. As
shown in FIGS. 3 and 4, the width 36 of the laser beam 32 is equal
to the width 2 of the wall 14, but the width 36 may be less than
the width 2. Because the width 36 of the laser beam 32 is that at
which the intensity drops to less than about 2-3% of its peak
value, the laser beam width includes a maximum intensity portion
sufficient to form a sealed portion 6 in the wall 14 and lesser
intensity portions that do not form a sealed portion 6 in the wall
14. Accordingly, the width 3 of the sealed portion 6 produced by
the laser beam 32 is less than the width 36 of the laser beam 32,
and is less than the width 2 of the wall 14. Accordingly, unsealed
portions 7 and 8 are disposed on either side of the sealed portion
6, as shown in FIGS. 3 and 4.
[0062] Laser beam 32 is traversed relative to the display device 10
so as to follow the path of the wall 14. Relative motion between
display device 10 and the laser beam 32 may be accomplished by
moving display device 10 relative to the laser beam 32, or moving
the laser 31 (and therefore the laser beam 32), relative to the
display device 10. For example, the laser 31, or the display device
10, may be mounted to a stage movable in an x-y plane. The stage
can be, for example, a linear motor stage whose movement may be
computer controlled. Alternatively, both the display device 10 and
the laser 31 may be stationary, and the laser beam 32 moved
relative to the display device 10 by directing laser beam 32 from
the laser 31 to one or more movable reflectors (mirrors) controlled
(moved) by galvometers. The speed of travel of the laser 31 (or
laser beam 32) relative to the wall 14 can range from between about
0.5 mm/s to as much as 300 mm/s, although a speed of between 30
mm/s and 40 mm/s is more typical. The power necessary from the
laser beam 32 may vary depending on the optical absorption
coefficient .alpha. and thickness 1 of wall 14. The necessary power
is also affected if a reflective or absorbent layer is placed
beneath wall 14 (between wall 14 and substrate 16) such as
materials used to fabricate electrode(s) 20, and by the speed of
traverse of laser beam 32 relative to the wall 14.
[0063] Additionally, the composition, homogeneity and filler
particle size of the frit used to make wall 14 can vary. This, too,
can adversely affect the way the wall absorbs the optical energy of
laser beam 32. As laser beam 32 is traversed to follow the path of
the wall 14, a portion of the wall 14 melts to form sealed portion
6 that forms a hermetic seal in the wall 14 and between the
substrates 12 and 16 thus sealing the substrates one to the other.
The gap between substrates 12 and 16 caused by the sealed portion 6
forms a hermetic pocket or envelope for OLED element 18. It should
be noted that if second substrate 16 is transparent at the sealing
wavelength, sealing may be performed through second substrate 16,
or both substrates 12 and 16.
[0064] The delivery system 30 may include lenses or other optics,
mirrors or reflecting elements, and may also include a single core
fiber to direct the laser beam 32. In the embodiment shown in FIG.
2, the delivery system 30 includes a lens 38, reflectors (mirrors)
40, 42, 44, a first coupling section 46, and a second coupling
section 48. The reflectors 40, 42, 44 can partially reflect and
partially transmit energy waves as appropriate, as is known in the
art, so as to allow the energy waves to pass to various devices
connected to the delivery system 30.
[0065] A beam from laser 31 is reflected by reflector 40 so as to
travel through lens 38 and emerge as laser beam 32 that is directed
toward display device 10. The laser beam 32 may be directed by a
single core fiber disposed between the lens 38 and the display
device 10.
[0066] Sealing with the Wall Thickness Within the Depth of Focus of
the Laser Beam
[0067] In one embodiment, the lens 38 focuses the laser beam 32
from laser 31 so that the thickness 1 of the wall 14 is disposed
within the depth of focus 34 of laser beam 32. The depth of focus
34 is the distance over which the focused laser beam 32 has
substantially the same intensity, as described below. Generating a
laser beam 32 so that its beam waist 37 is at or near the focal
point increases the depth of focus 34 thereby providing higher
tolerances for alignment and vibration leading to a more uniform
seal. The beam waist 37 is the portion of the laser beam having a
minimum width.
[0068] FIG. 5 illustrates the parabolic variation of the laser beam
width with distance for a Gaussian beam, and a definition of Depth
of Focus (DOF) 34.
[0069] Specifically, the relationship between beam width and
distance is as follows:
( w w o ) 2 = 1 + ( z z o ) 2 ##EQU00001## [0070] wherein: [0071] w
is beam width; [0072] w.sub.o is beam width at the focal point;
[0073] z is distance from the focal point of lens; and [0074]
z.sub.o is the transition point between the near-field of the lens
38 and the far field of the lens 38.
[0075] Further, the DOF is defined as:
DOF = ( 8 .lamda. .pi. ) ( F D ) , ##EQU00002##
wherein: [0076] F is focal length of the lens 38; [0077] D is the
diameter of the laser beam on the lens 38; and [0078] .lamda. is
the wavelength of the laser.
[0079] In the far field, the beam width varies linearly with the
distance from the focal point. On the other hand, in the near
field, the beam width varies parabolicly with the distance from the
focal point and has a minimum, i.e., a beam waist 37, at or near
the focal point.
[0080] Around this focal point, within the depth of focus DOF 34,
the beam width 36 does not experience great changes. As the beam is
defocused away from the focal point F the beam width starts to
change very rapidly requiring exact positioning in order to achieve
a desired beam width value.
[0081] Therefore, producing sealed portion 6 in the wall 14 by
placing the wall thickness 1 within the depth of focus 34,
regardless of the shape of the footprint 35 of the laser beam 32,
is advantageous because such operation is more insensitive to
mechanical misalignments and vibrations, i.e., to changing
distances between the delivery system 30 and the display device 10.
However, operation within the depth of focus is less flexible in
the sense that the beam width 36 will be fixed based on the lens
arrangement used. Nonetheless, different beam widths 36 may be
produced by changing the lens 38 and/or the diameter of the laser
beam on the lens 38.
[0082] For example, for one lens system according to this
embodiment, the beam width was plotted against the distance from
the focal point. See FIG. 6. The beam was a flat-top beam having a
waist of 1 mm. As shown in this figure, the beam width remains
about 1 mm as the distance from the focal point ranges from 0 to
about 3 mm. That is, the DOF 34 is around 6 mm. Because the
thickness 1 of the wall 14 is on the order of up to hundreds of
microns, a DOF 34 of 6 mm allows for a significant amount of
variation in distance between the delivery system 30 and the
display device 10, while maintaining the thickness 1 of the wall 14
within the DOF 34 of the laser beam 32 so as to produce a uniform
seal.
[0083] Additionally, operating within the DOF 34 of the laser beam
32 offers another advantage. Specifically, an imaging device and/or
thermal monitoring device can be implemented through the same
delivery system 30 as used for the laser 31, thus improving the
capability of the sealing process control feedback, reducing time
for development of the optimal regime for sealing conditions. The
imaging system and thermal monitoring systems can be used
independently of one another, in conjunction with one another, or
not at all.
[0084] As shown in FIG. 2, the delivery system 30 may include a
first coupling section 46 to which an imaging device 50 is
connected. The imaging device 50 may be a charge couple device
(CCD), a complementary metal oxide semiconductor (CMOS) device, or
a junction field effect transistor (JFET) device, for example. When
the thickness 1 of the wall 14 is disposed within the DOF 34 of the
laser beam 32 as propagated through lens 38, an image of the
display device 10 may be captured by imaging device 50, via
reflector 42 and lens 38.
[0085] As also shown in FIG. 2, the delivery system 30 may include
a second coupling section 48 to which a thermal monitoring device
60 is connected. The thermal monitoring device 60 may be a
pyrometer, a bolometer, or a thermal camera, for example. When the
thickness 1 of the wall 14 is disposed within the depth of focus
34, it is a simple matter to capture thermal information through
the lens 38 via reflector 44.
[0086] Laser Beam Width Relative to Wall Width
[0087] In another embodiment, the laser beam width 36 may be sized
by the delivery system 30 so as to eliminate the need for a mask
disposed adjacent to the wall 14. Elimination of a laser mask may
reduce cost and improve efficiency of laser sealing.
[0088] A mask can be eliminated by choosing an appropriate laser
beam width 36 relative to the width 2 of the wall 14 to be sealed.
More specifically, the laser beam width 36 is chosen so as to be
less than or equal to the width 2 of the wall 14. In this case, not
100% of the wall width will be sealed. However, by dispensing frit
to form a wall 14 that is as wide as, or wider than, the width 36
of the laser beam 32, the width 3 of the sealed portion 6 itself
can be maintained the same size as that obtained by having a wall
width 2 sized to the 2.omega. diameter of a conventionally masked
laser beam. In other words, the excess wall width 2 itself acts as
a mask. Further, because mechanical strength and hermeticity are
determined by seal width 3, the integrity of the seal 6 remains the
same as that for a conventionally made seal. Accordingly, in terms
of hermeticity and mechanical strength, the excess wall width does
not make any noticeable impact.
[0089] In a display device 10, the space available for sealing is
typically larger than the width of the frit typically dispensed.
For example, for a 2'' device, a sealing space of 1.2-1.4 mm is
typically available, yet the width of frit typically dispensed is
0.7 mm. This means that frit can be dispensed to form a wall 14
that is wider than that conventionally dispensed by utilizing more
of the space available for sealing. Then, if the laser beam width
36 is chosen to be less than or equal to the width 2 of the wall
14, no laser mask will be needed.
[0090] For example, as shown in FIG. 7, a Gaussian beam was chosen
to have a width 36 substantially the same as the 2.8 mm dispensed
frit width (corresponding to the width 2 of the wall 14). In FIG.
7, it is seen from the laser beam intensity profile 33 that the
laser beam has a width 36 substantially equal to the width 2 of the
wall 14. As noted above, the width 36 of the laser beam 32 is the
width of the laser beam 32 at the point wherein the intensity drops
to less than about 2-3% of its peak value. The laser beam width
includes an intensity profile 33 having a maximum intensity
portion, i.e., that portion of laser beam profile 33 within the
cross-hatched area of FIG. 7, sufficient to form a sealed portion 6
in the wall 14. Also, the laser beam width includes lesser
intensity portions, i.e., those portions of laser beam profile 33
outside the cross-hatched area of FIG. 7, that do not form a sealed
portion 6 in the wall 14. Accordingly, the width 3 of the sealed
portion 6 produced by the laser beam 32 is less than the width 36
of the laser beam 32, and is less than the width 2 of the wall 14.
Unsealed portions 7 and 8 are disposed on either side of the sealed
portion 6.
[0091] After heating with the Gaussian beam, the width 3 of the
sealed portion 6 was about 1 mm. Thus, the sealed portion 6 has a
width 3 of about 35.7% of the width 2 of the wall 14. The unsealed
portions 7, 8 of the wall 14 thus act as a mask to shield the OLED
element 18 and electrodes 20 of the display device 10 from damage
by the laser beam 32. Because the wall 14 is sintered prior to
heating it with the laser beam 32, there is no loose frit remaining
in the display device 10, even though the entire width of the wall
14 does not form sealed portion 6. The 1 mm wide seal width 3 is
similar to that of conventional seals and, thus maintains the same
hermeticity and mechanical strength as conventionally sealed
display devices.
[0092] By using a flat-top beam, as described above, a higher seal
ratio can be obtained than with a Gaussian beam. Thus, a similarly
sized wall width 2 will produce a larger seal width 3. See, for
example FIG. 8, wherein a dispensed frit width of 2.2 mm
(corresponding to the width 2 of the wall 14) resulted in a seal
width 3 of 1.6-1.7 mm when using a flat-top beam of generally the
same width 36 as the width 2 of the wall 14. For example, in FIG.
8, it is seen from the laser beam profile 33 that width 36 is
substantially equal to the width 2 of the wall 14. As noted above,
the width 36 of the laser beam 32 is the width of the laser beam 32
at the point wherein the intensity drops to less than about 2-3% of
its peak value. The laser beam width includes an intensity profile
33 having a maximum intensity portion, i.e., that portion of laser
beam profile 33 within the cross-hatched area of FIG. 8, sufficient
to form a sealed portion 6 in the wall 14. Also, the laser beam
width includes lesser intensity portions, i.e., those portions of
laser beam profile 33 outside the cross-hatched area of FIG. 8,
that do not form a sealed portion 6 in the wall 14. Accordingly,
the width 3 of the sealed portion 6 produced by the laser beam 32
is less than the width 36 of the laser beam 32, and is less than
the width 2 of the wall 14. Unsealed portions 7 and 8 are disposed
on either side of the sealed portion 6.
[0093] Similarly, with a flat-top beam frit can be dispensed into a
smaller wall width 2 than for a Gaussian beam and yet the same seal
width 3 can obtained. As shown in FIG. 9, when using a flat-top
beam, a dispensed frit width of 1.3 mm (corresponding to the width
2 of the wall 14) resulted in the same 1 mm seal width 3 as for the
Gaussian beam used on a dispensed frit width of 2.8 mm (as shown in
FIG. 7). In FIG. 9, it is seen from the laser beam profile 33 that
the laser beam width 36 is substantially equal to the width 2 of
the wall 14. As noted above, the width 36 of the laser beam 32 is
the width of the laser beam 32 at the point wherein the intensity
drops to less than about 2-3% of its peak value. The laser beam
width includes an intensity profile 33 having a maximum intensity
portion, i.e., that portion of laser beam profile 33 within the
cross-hatched area of FIG. 9, sufficient to form a sealed portion 6
in the wall 14. Also, the laser beam width includes lesser
intensity portions, i.e., those portions of laser beam profile 33
outside the cross-hatched area of FIG. 9, that do not form a sealed
portion 6 in the wall 14. Accordingly, the width 3 of the sealed
portion 6 produced by the laser beam 32 is less than the width 36
of the laser beam 32, and is less than the width 2 of the wall 14.
Unsealed portions 7 and 8 are disposed on either side of the sealed
portion 6.
[0094] With each of the FIG. 8 and FIG. 9 arrangements, the seal
width 3 was about 77% of the width of the dispensed frit
(corresponding to the width 2 of the wall 14). A flat-top beam can
be generated using all-refractive optics lens system based on IBM
patented technology and offered by Newport Corporation, of Irvine,
Calif. Accordingly, use of a flat-top beam allows greater design
freedoms in that either a higher percentage seal (and thus stronger
seal) may be obtained in the same space, or that a lower footprint
wall (i.e., having a smaller width 2) may be used to obtain the
same seal strength (as corresponds to the width 3 of the seal 6),
as obtained with a Gaussian beam.
[0095] From the above examples, it is seen that a seal width 3 of
from about 35.7% to about 77.3% of the width 2 of the wall 14 (for
example 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64,
66, 68, 70, 72, 74, 76 and 77%) can maintain a successful hermetic
seal. Preferably, the seal width 3 is from about 50% to about 75%
of the width 2 of the wall 14, for example 52, 54, 56, 58, 60, 62,
64, 66, 68, 70, 72, and 74%.
[0096] Any of the beam shapes in this disclosure may be used
without a mask in the manner described above, i.e., wherein the
width 2 of the wall 14 is equal to or larger than the width 36 of
the laser beam 32. It is preferable to have the width 2 of the wall
14 sized relative to the footprint 35 of the laser beam 32
(including beam width 36) so that when the laser beam 32 traverses
a corner or a curved portion of the wall 14, the laser beam
footprint 35 remains within the edges 4, 5 of the wall 14, i.e., so
that the laser beam 32 does not cause damage to portions of the
display device 10 that are near the wall 14, for example,
electrodes 20 or OLED element(s) 18. When using a laser beam width
36 as described above, the sealed portion 6 of the wall 14 will
generally be located such that there are unsealed portions 7, 8 on
either side of the sealed portion 6. See, for example, FIGS. 1 and
3.
[0097] Laser Beam Intensity Profile
[0098] Operating within the depth of focus 34 produces a hermetic
seal in wall 14 that is just as strong as one produced by a
defocused laser beam. Further, by selecting an appropriate laser
beam intensity profile, a reduction in power may also be achieved
while still maintaining the same seal strength.
[0099] FIG. 10 shows data regarding probability of failure based on
load testing dozens of samples sealed. Generally, the samples were
prepared according to the above-described preparation process, and
then sealed with different laser configurations. Specifically, frit
was deposited to form a wall 14 on first substrate 12, subjected to
sintering, and then disposed on second substrate 16 so that the
wall 14 was disposed between the substrates. The walls 14 of
different samples were then heated with the different laser
configurations to form a hermetic seal between the substrates 12,
16. The resulting glass packages were subjected to a four-point
load to determine probability of failure at various loading
conditions.
[0100] The samples in the graph of FIG. 10 were sealed using either
a Gaussian beam or a flat-top beam as described below, and with
scaling of the beam width 36 relative to the wall width 2.
Specifically, the width of the Gaussian beam was sized to 1.8 times
the frit width, and the width of the flat-top beam was 1.65 times
the frit width. Here a frit width of 0.7 mm was deposited to form a
wall 14 having a corresponding width 2.
[0101] The different laser configurations were as follows.
[0102] Data points shown by triangles are for devices sealed with a
standard defocused Gaussian beam made with a laser at 810 nm and 30
W. Data points shown by squares are for devices sealed with a
defocused Gaussian beam made with a laser at 913 nm and 28 W. Data
points shown by circles are for devices sealed with a focused
flat-top beam made with a laser at 913 nm and 25 W. The laser was
not a perfect flat-top beam because it still had some tails on the
optical field near the edges.
[0103] As can be seen from the distribution of data points in FIG.
10, the samples sealed with the defocused Gaussian beam of 913 nm
and 28 W (square data points) had a very similar probability of
failure distribution as those made with the defocused Gaussian beam
operating at 810 nm and 30 W (triangle data points). Each
distribution experienced a significant rise in the probability of
failure at a load of between 16 and 17 Kgf; note the almost
vertical increase in failure probability over this range of force
increase. Accordingly, the change from 810 nm to 913 nm, and
resulting reduction in power, did not affect the seal strength.
[0104] Similarly, the samples sealed with the focused flat-top beam
of 913 nm and 25 W (circle data points) had a very similar
probability of failure distribution as those made with the
defocused Gaussian beam operating at 913 nm and 28 W. Again, each
distribution experienced a significant rise in the probability of
failure at a load of between 16 and 17 Kgf; note the almost
vertical increase in failure probability over this range of force
increase. Accordingly, the samples sealed with the focused flat-top
beam, using less power, did not affect the seal strength relative
to the defocused beams of higher power.
[0105] Specifically, the 913 nm defocused Gaussian beam was sealed
at 28 W while the flat top beam was sealed at 25 W, resulting in a
reduction of 11% in power for the flat top beam; and a reduction of
17% in power for the flat top beam as compared to the 810 nm
defocused Gaussian beam at 30 W. These two sets of samples sealed
with different beam intensity profiles and power were tested for
mechanical failure and, as noted above, in practice they presented
the same probability of failure. This confirms that despite the
power reduction found due to the laser beam characteristics, i.e.,
focused flat-top beam versus defocused Gaussian beam, the finished
sealed sample had very similar mechanical properties. Accordingly,
it is advantageous to use a focused flat-top beam. That is, there
is likely to be less damage to the device elements and to the wall
14 itself due to the lower power. Overall, beneficially, less
energy is deposited in the process.
[0106] The reduction in power from use of the flat-top beam can
significantly benefit the sealing process and produce less damage
for the device elements and the display devices 10 themselves. The
reduction in power is based on a more uniform distribution of the
power density across the wall 14.
[0107] If a less uniform laser beam intensity profile is used in
order to achieve a maximum seal width, the central part of the wall
14 will be overheated as seen in a seal image as so called "laser
track", because the intensity near the center of the laser beam
footprint 35 is greater than the intensity at the edges of the
laser beam footprint 35. In addition to using a flat-top beam, in
order to provide a more uniform profile, because the laser beam 32
moves, one also needs to consider that different locations of the
wall 14 away from the center and towards its edges 4, 5 would have
a different time of exposure. For this reason, the laser beam
footprint 35 on the wall 14 instead of being circular may be closer
to square shape, or one wherein the area near the center-portion 39
of the footprint 35 is less than the area on either side of the
center-portion 39. The center-portion 39 of the footprint 35 spans
about one third of the width 36 of the footprint 35, leaving areas
on either side that each also span about one third of the width 36
of the footprint 35. See FIGS. 11-14, wherein FIG. 11 shows a
circular footprint 35, FIG. 12 shows a square footprint 35 (area of
the center-portion 39 of the footprint 35 is less than the area on
either side of the center-portion 39), FIG. 13 shows a cross-shaped
footprint 35, and FIG. 14 shows a square-in-square footprint 35. In
FIGS. 13 and 14, the footprint 35 has an area of the center-portion
39 that is less than the area on either side of the center-portion
39. In the case of FIGS. 13 and 14, the exposure and power
intensity applied to the wall 14 at different distances in the
x-axis direction from the center of the wall 14 would be the same
because the greater area on either side of the center-portion 39 of
the footprint 35 compensates for the reduced intensity in that same
area. Similarly, the reduced area of the center-portion 39 of the
laser beam footprint 35 reduces the energy applied to the wall 14
by the portion of the laser beam having the greatest intensity. It
is expected that a more flat laser beam intensity profile 33 used
with the footprints 35 of FIGS. 12-14 would require less power for
sealing to achieve a maximum seal width. However, in addition to
the laser beam footprints 35 of FIGS. 12-14, circular footprints 35
(See FIG. 11) are also possible, as described later.
[0108] The laser beam footprints 35 may be selected so that they
produce a uniform temperature distribution (heating profile) across
the wall 14, as the laser beam 32 follows the path of the wall
14.
[0109] As shown in FIG. 4, the width of the wall 2 extends parallel
to the x axis, and the laser beam footprint 35 translates in the
direction of the y axis, with its width 36 extending substantially
parallel to the x axis. In FIG. 4, the coordinate axis is shown for
simplification of explanation only.
[0110] The equation showing the heating profile across the wall 14
is as follows:
T(x)=.intg.(I(x,y)*L(y)/v)dy,
where x is distance from center line of the frit, T(x) is
temperature as function of x, I(x, y) is the distribution of the
laser beam 32 intensity, which should be symmetrical relative to x
and y, L(y) is the cross-section of the beam width at location x,
and v is linear velocity of the beam translation. This equation
neglects diffusion of heat in the x, y plane due to low heat
diffusivity of the material from which the wall 14 is made. If heat
diffusion takes place in the x, y plane, corresponding adjustments
of the beam shape may be needed to make the resulting T(x) uniform
as a function of x.
[0111] The laser footprints 35 of FIGS. 11-14 can be produced with
an aperture, similar to that disclosed below in connection with
FIGS. 15 and 16, or with diffractive optics, as is known in the
art. By producing the shapes in these manners, the laser beam 32
can be delivered through a solid core and, therefore, avoid hot
spots, or spikes in its profile, as when a focused beam is
delivered through a fiber bundle. Diffractive optics that can be
used to produce the footprints 35 shown in FIGS. 9-14 are available
from RPC Photonics, of Rochester, N.Y. By producing the shapes with
diffractive optics, or apertures, the delivery system 30 can still
operate so that the thickness 1 of the wall 14 is located within
the depth of focus 34 of the laser beam 32. These laser beam
footprints 35 may be used in conjunction with other features and
embodiments as disclosed herein.
[0112] Shaping the Laser Beam with an Aperture
[0113] In this embodiment, shaping the laser beam with an aperture
allows the use of a Gaussian beam with reduced power to
successfully provide a hermetic seal. FIGS. 15 and 16 show a manner
of shaping the laser beam 32 with the use of an aperture 74 in a
beam-shaping plate 70. Here, beam-shaping plate 70 is coupled to
the delivery system 30 via a coupling member 72, so that the
beam-shaping plate 70 moves along with the laser beam 32 as the
laser beam 32 follows the path of the wall 14. The coupling member
72 may be a hollow tube or other mechanical coupling structure. The
inside of the coupling member 72 may have a light-absorbing surface
to minimize light scattering. The aperture 74 shapes the laser beam
32 as the beam passes therethrough. The aperture 74 has a width 76
that is sized to be less than, or equal to the width 2 of the wall
14. During a sealing operation, the beam-shaping plate 70 is placed
in close contact with the first substrate 12, and the laser beam 32
is made to follow along the path of the wall 14. Laser energy
passing through the aperture 74 heats the wall 14 and forms a
sealed portion 6 in the wall 14. In contrast to conventional masks,
the beam-shaping plate 70 does not cover the entire first substrate
12, but instead operates to shape the laser beam footprint 35.
[0114] In one example, a wall 14 having a width of 1.2 mm was
sealed with a Gaussian beam of 60 W before passing through the
beam-shaping plate 70 and aperture 74. The aperture width 76 was
set at 1.1 mm, and allowed a power of about 20 W to leak through to
the wall 14. The laser beam 32 was moved at 10 mm/s relative to the
wall 14, and the resulting seal width 3 was 1.1 mm.
[0115] The beam-shaping plate 70 may be used in connection with any
of the other laser configurations described herein, and may be
disposed within the depth of focus 34 of the laser beam 32.
Alternatively, the beam-shaping plate 70 may be used with other
laser systems not disclosed herein. Additionally, the aperture 74
may be configured so as to have any shape, for example shapes
matching the laser beam footprints 35 shown in FIGS. 8-11, and
still allow the laser apparatus 30 to operate so that the wall 14
lies within the depth of focus 34 of the laser beam 32.
[0116] It should be emphasized that the above-described embodiments
of the present invention, particularly any "preferred" embodiments,
are merely possible examples of implementations, merely set forth
for a clear understanding of principles of the invention. Many
variations and modifications may be made to the above-described
embodiments of the invention without departing substantially from
the spirit and principles of the invention. All such modifications
and variations are intended to be included herein within the scope
of this disclosure and the present invention and protected by the
following claims.
* * * * *